During the construction of many different structures, such as airplanes, it is necessary to provide suitable grounding for the electronics and electrical systems. It is particularly critical for airplane construction, because airplanes, in addition to requiring a robust ground reference for their electrical systems, are also subject to outside electrical phenomenon, such as lighting and stray electromagnetic energy (EME), such as from radars or the like. In the past, the metallic wing structure of an airplane provided a grounding system and overall attachment point for ground references. However, with the advent and growing popularity of composite wing structures, it has been necessary to provide an alternate grounding system.
Currently, the airplane frame is used to provide a grounding reference and an attachment point for various ground busses in the electrical system of the aircraft. The most common method for making such a connection is to use a lug. A lug is a device having an open end or sleeve for receiving an end of a tubular wire or other conductor. The other end is a flattened portion with a hole to connect the lug to a flat surface. The sleeve of the lug is slid over the end of the tubular conductor and then a crimping pliers, an adhesive, welding, or other similar techniques are used to connect the lug to the conductor. The lug is thus attached to the conductor and the flat end is positioned to rest upon the flat surface of a frame portion or other support structure. The hole in the flat surface enables a fastener or bolt to pass through to firmly fix the tubular structure to the flat surface.
Traditional lugs have many drawbacks. First, a weakness exists between the conductor cable and the open end or sleeve of the lug. For example, the conductor may pull out of the lug. Furthermore, the stress on the conductor at the crimp might cause the conductor to break at that point. Additionally, potential for less than optimal performance exists. Oftentimes, the lug is made of a different metal than the conductor and corrosion may occur between the dissimilar metals. Furthermore, the lug-to-cable interface is often subject to corrosion due to moisture. This may lead to premature corrosion failure of the cable. Also, the crimped lug may not provide a good low resistance or low impedance path through the end of the conductor. Still further, for attachment of the lugs along a long length of cable, it is necessary to cut the cable, attach two lugs to the cut end, and then bolt the two lugs to the frame or other structural element. As may be appreciated, such additional steps are time consuming and costly. Also, as may be appreciated, it is undesirable to provide a break or cut in the length of the cable.
Therefore, many needs exist in this area of technology, particularly with respect to providing a robust ground reference in an airplane.